ANTIBODIES TO DIPHTHERIA, TETANUS AND PERTUSSIS IN INFANTS BEFORE ANDAFTER IMMUNIZATION WITH DTP (TRIPLE ANTIGEN) VACCINE

Objective: To determine antibody levels to the Australian manufactured combined diphtheria, tetanus and pertussis (DTP) vaccine (Triple Anti gen, CSL Ltd) in infants before and after their primary immunization c ourse. Methodology: Serosurvey (antibody prevalence study) in two grou ps: infants aged 5-9 weeks who had not received any immunizations (n = 25), and infants aged 7-10 months who had received two (n = 25) or th ree immunizations (n = 57) with DTP, sampled from infants attending th e Royal Children's Hospital, Melbourne, either as inpatients or outpat ients between February and April 1993. The immunization history for ea ch infant was determined from hospital records, the parent-held child health record, or the local council or family doctor who immunized the infant. Results: Enzyme immunoassay (EIA) of antibodies to diphtheria and tetanus showed all infants to have adequate protective levels aft er two or three vaccinations (greater than or equal to 0.01 IU/mL). Al l subjects who had received all th ree DTP vaccinations had detectable antibody to at least one pertussis antigen. Antibodies to the pertuss is antigens filamentous haemagglutinin and pertussigen (pertussis toxi n) were comparable to levels determined for whole cell pertussis vacci nes used elsewhere in the world. EIA-determined antibodies to pertussi s agglutinogen type 2 and agglutinogen type 3 showed substantially hig her geometric mean titres when results for pre-immunization and post-i mmunization subjects were compared. Conclusions: These data show that the Australian manufactured DTP vaccine has immunogenic properties sim ilar to those of vaccines used elsewhere, and that antibody concentrat ions following immunization are at levels consistent with efficacy.